Heated steering wheel wires - POS & NEG?

[jpilk99]

Hi all,

I'm about to put a heated steering wheel on my '01 740iL; (which did not come with one originally). I have two good heated wheels, the correct buttons, slip-ring, air bag, internal wiring, etc. My big question is:

For the 2 wires that feed the back of the slip ring - can someone tell me which is the POS and which is the NEG? One is Light Green with black stripe and the other is Brown. Historically, usually wires with the black stripe are NEG, but, just want to be sure. I thought I recalled someone saying that it didn't matter which was POS and NEG but that seems iffy to me.

Also, if anyone has wired this up and has a suggestion for a good 'switched' POS to jump/splice off of, that would be great to know as well.

Thanks all.

Jay

[TheAngryBear]

BMW used brown for the ground (neg).
Validate by looking at the battery cables.


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[jpilk99]

BMW used brown for the ground (neg).
Validate by looking at the battery cables.

Thanks AngryBear. Just to confirm, are you saying that the color of the battery cables indicate similar polarity throughout the vehicle? My NEG cable in the trunk at the battery is Brown, so that means the Brown at the heated wheel is NEG too? Also at the battery, POS is obviously Red... so by the same logic, shouldn't the POS wire for the heated wheel be Red too?

Just want to make sure I understand. Thanks.

[TheAngryBear]

BMW uses brown as the ground color throughout the vehicle.
Solid Red (like battery cable) is always positive and serves no other function than to provide voltage. Normally these solid red cables are always active regardless of key position or start.
Other lines will provide switched power, carry signal/comms, etc. These are dependent on key position, other switches, engine start, etc.
so it doesn’t surprise me the pos there is non-solid red. Why run constant power to that assembly?
Hope that makes sense...


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[Narlift]

2nd for brown as ground. good luck!

[jpilk99]

Thanks all. Brown is ground (got it). Red is constant-ON positive ( got it ).

So, anything not-red or not-brown is switched-on?

Thanks again.


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[TheAngryBear]

So, anything not-red or not-brown is switched-on?

Sort of.
It can be many things: switched on, signal/data line, voltage variable, etc.
you need the schematics to determine if it is switched power or something else.


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[jpilk99]

I finally jumped back into this project again today: trying to swap out a non-heated steering wheel with a heated one ...and trying to make it work; heat up . But, it ain't going so good and I'm hoping someone can shed light on what I'm doing wrong. Some points:

• I tried this swap last year around this time but couldn't make it work. I got a slip ring from a car with heated steering and already installed that.
• I have wired in a POS & NEG wire, (tested both). But, when I tried this last year, it didn't work so I assume I had the POS & NEG reversed. As well, looking at the wiring that sits in the center/middle of the steering wheel when you remove the airbag, of the 2 wires for the heated wheel - the Brown, which splits and feeds another circuit, goes to the 4 wires of the heating elements IN the circumference of the wheel. So, I believe that needs to be the POS. (However, now I'm all confused about the previous post(s) about Brown being ground...).
• I have 2 heated steering wheels and tested the wiring on both and got the same results of the outer 2 wires being 0 resistance and the inner 2 having low resistance. Again, both performed the same way, so (assuming it's unlikely they'd both perform the same) I believe both are good.
• After having the battery disconnected the entire time, I installed the replacement wheel and connected the wiring. I reconnected the battery and went to test. (Oddly, I can't seem to turn the key to the second position and have all lights come on WITHOUT the car starting. Not sure what I did, taking the plastic housing off under & above the steering column, but, ...I'll deal with that when I'm done with the heated wheel). So, with the car running, I hit the "heated steering wheel" button and ...nothing. No light, no heat. I turned the car off, turned the key again to get all the lights on and it started again ...but still, no heated steering wheel.
• Disconnected battery again, took off air bag, disconnected wiring connectors ...and tried a second air bag with completely new sets of buttons (volume, radio presets, cruise, etc. ...thinking maybe it's the button on the other air bag). Connected everything, put it all back together, reconnected battery, turned key ...car started, no heated steering wheel.
• Both times, with both air bags and buttons, I tested the volume, radio preset changer, cruise, etc. and all buttons function as they should. Except heated wheel.

Only thing I can think of is maybe I have the POS & NEG reversed. But, as some of the previous comments in this thread state, "brown" is POS. As well, I can see the wiring harness inside the center of the steering wheel when you take the airbag off, that the brown wire goes over to the heating element(s) wiring connector... So, I believe I have POS coming into the correct pin of the slip ring. I guess I could swap it and see, but, ...I had it backwards the last time I tried and swapped it today.

Any guidance is GREATLY appreciated. It's cold out and I'd love for this heated wheel to work. Thank you!

Jay

[Timm]

BROWN is negative - it always is on BMW cars - and a check on the WDS for steering wheel heating shows that is the case. RED at the ribbon is positive. It is worth saying that there are electronics in the steering wheel to control the heating element - and they will not like being reverse polarised!

[jpilk99]

BROWN is negative - it always is on BMW cars - and a check on the WDS for steering wheel heating shows that is the case. RED at the ribbon is positive. It is worth saying that there are electronics in the steering wheel to control the heating element - and they will not like being reverse polarised!

Looks like I"m going back to the junk yard to get another "steering wheel wiring" harness for behind the air bag. It's the only thing I can think of at this point - though I did take the harness apart and inspect the little circuit board and saw now visible damage to having the POS & NEG reversed. But again (and I know this post is a year old) I had the POS & NEG correct the last time I tried this and it didn't work. I believe both wheels work, though I never had them working in a car; (bought one at the junk yard and the other here on the forum). Since the heating element in both wheels performs the same to continuity tests, I believe they are both working fine....

Who knew a heated steering wheel could be so tough

[acspecialists]

You could put power directly to the elements, polarity won't matter. Based on your readings they may not be good. Each coil should have some resistance, if the reading is zero it would be shorted. Make sure the scale on your meter is set low. If there is a shorted coil every time you put power to it you will fry something.

[racer2086]

Few things to know about the heated wheel:

From the factory, switched power is pulled straight from the ignition switch, to the fuse box, through a fuse, back to the wheel. So you can get power from pin 10 (I think it was pin 10? -- it was empty on my car since it didn't have a heated wheel from the factory) from the ignition switch, but you must put a fuse in line. Check the WDS wiring schematic for the correct pin number.

Second, the power is not fed directly to the heating element. The button pod with the heating button controls the power to the element.

The element has a sensor in it to tell the button pod what temperature the wheel is. The button pod not only has to sense this sensor, but also sense that the heating element isn't shorted or open.

It is a very simple set up, so if you are having trouble, take a step back, take everything out, and start from scratch. You NEED to look at the WDS wiring diagram if you don't see how it goes together.

And I wouldn't feed power straight to the wheel heater, because I'm not sure if that will burn it out. The button pod may have a resistor and other electronics in it to control the amperage that ends up at the heating element.

[jpilk99]

Few things to know about the heated wheel:

From the factory, switched power is pulled straight from the ignition switch, to the fuse box, through a fuse, back to the wheel. So you can get power from pin 10 (I think it was pin 10? -- it was empty on my car since it didn't have a heated wheel from the factory) from the ignition switch, but you must put a fuse in line. Check the WDS wiring schematic for the correct pin number.

Second, the power is not fed directly to the heating element. The button pod with the heating button controls the power to the element.

The element has a sensor in it to tell the button pod what temperature the wheel is. The button pod not only has to sense this sensor, but also sense that the heating element isn't shorted or open.

It is a very simple set up, so if you are having trouble, take a step back, take everything out, and start from scratch. You NEED to look at the WDS wiring diagram if you don't see how it goes together.

And I wouldn't feed power straight to the wheel heater, because I'm not sure if that will burn it out. The button pod may have a resistor and other electronics in it to control the amperage that ends up at the heating element.

Thanks Racer. Here is the WDS I have for this. My question is: How to figure out where the issue may be?

1. I know I have switched-power coming in on the right pin, (on that 2 pin connector on the left), as you look at the slip ring from the drivers' seat without the wheel on. The left pin is ground.
2. This corresponds to the 2 wire connector as part of the little wiring harness that sits behind the steering wheel in front of the slip ring, with the Red wire getting POS and the Brown getting NEG.
3. I can see that the Brown wire gets spliced into 2 Brown wires; one going directly to the 4-wire connector of the heating element(s) in the wheel and the other feeds into the white plastic "harness" with the little 1"x2" circuit board. The Red goes directly into the circuit board.
4. No Red comes out of the circuit board, however, the 2 Black wires and 1 Black w/White Stripe that come out of the circuit board and are the other 3 wires in the 4-wire connector to the heating elements of the wheel. Again, not sure the sequence of events, i.e. "Press button on steering wheel, sends signal to circuit board which then ...1. turns on green indicator light on button and 2. sends power to heating element(s) ...which is then monitored back in the circuit board and heat turned off/on as needed...".
5. Lastly, and forgive me if I'm repetitive, but, when I use my ohmmeter on the 4-wire connector to the heating element in the wheel, I get:

• Zero resistance when I test the 2 outer-most wires together, the Brown and one of the solid Black wires.
• Minor resistance when I test the 2 inner wires, Black and Black w White Stripe. I get the same results with another heated wheel I have. I don't know if both are working correctly or if both are failing similarly. I have never seen either wheel work - bought one here on the forum and the other from the junk yard.

The only possible difference I can inject into this scenario is that I brought home a "new" control button pod off of a heated steering car. Now, I have 2 complete heated wheels & their airbags, however, I can't rule out that I may have fried something during my testing (as I did have POS & NEG reversed at one point).

But now with a new wiring harness and button pod, I'm hoping my next try at this will work. Fingers crossed.

[racer2086]

Ok, so first, you don't need to guess which wires you are measuring. They all have pin numbers written on the male and female connectors. They are very small, but if you look on the ends of the connectors and on the inside of the female connectors -- basically somewhere there are numbers -- you will see the pin numbers. That should make the schematic make much more sense to know what you're testing.

Based on the WDS diagram, pin 1 out of the slip ring is positive, and pin 2 is the ground. Also, the heating element is pin 1 and 2 on the 4-pin connector, the thermistor is pin 3, and pin 4 goes directly to ground.

There's really only two connectors you should have to hook up: the 2-pin slip ring connector and the 3-pin connector to the right button pod. Everything else should be assembled in the wheel.

Where are you getting your slip ring ground?

[jpilk99]

Here is a photo of where I tapped into ground.

[jpilk99]

Here is a photo of where I tapped into ground.

So, I just rechecked the resistance on the 4-wire connector going into the heating element and pins 1 & 2 is NOT a closed circuit, so that must mean the heating element is fried; hence the wheel is junk - as far as being a "Heated Steering Wheel"?

[racer2086]

Here is a photo of where I tapped into ground.

Well that would be your problem. I don't think that's a ground. Did you put a meter on it and check continuity from that wire to a known ground? I wouldn't think BMW would put a ground in the ignition switch. Just because it is black doesn't mean negative...

[acspecialists]

Brown in negative, look around the car and you will see a butt load of grounded wires. They will all be brown.

[jpilk99]

Well that would be your problem. I don't think that's a ground. Did you put a meter on it and check continuity from that wire to a known ground? I wouldn't think BMW would put a ground in the ignition switch. Just because it is black doesn't mean negative...

I did not - during this recent escapade of trying to get the heated wheel to work - check for continuity from the wire I tapped into to known ground. However, I would have thought I did when I first deemed it a useful "ground". I will confirm first thing in the morning.

Just curious though, I did test the POS wire I am using to feed the slip ring for the heated wheel with the NEG shown in the picture and ...it showed 12V. How could that happen without the POS being 12V and the ground being ..."ground"?

[racer2086]

Not sure, but I wouldn't use that wire as ground. I could guess and say that maybe you measured positive and negative with the key in the off position and that wire is not energized but rather grounded through the ignition switch in key position 0.

Regardless, that is a very thin gauge wire to be running a heating element through. Where did you get your positive power from?

[jpilk99]

Not sure, but I wouldn't use that wire as ground. I could guess and say that maybe you measured positive and negative with the key in the off position and that wire is not energized but rather grounded through the ignition switch in key position 0.

Regardless, that is a very thin gauge wire to be running a heating element through. Where did you get your positive power from?

Re the Ground wire, Racer, good call. It is NOT a constant Ground - only when the ignition is ON does is show NEG. Odd still that when you switch the ignition on, and it does become NEG and then when tested with the other pin, and it shows POS, that the circuitry would not work. All that said, I ran a new wire off of the frame and it is constant Ground.

Re the POS wire and "thin gauge", while I certainly would agree that it is thin, it is the same exact gauge as the wiring I took out of another '01 E38 with Heated Seat (see picture uploaded here). And I am getting 12V switched power...

Bottom line, none of the 2 heated wheels work. And at no time will the green light on the button pod turn on. Can't tell if it's:

• The wiring harness, with the white plastic & little 1"x2" circuit board, between wheel and airbag. I did try another one that I just removed from junk yard. Possible both are bad, but, don't know.
• The button pod. I tried the two airbag setups I have, and another button pod that I just brought home from junk yard, and none result in either the green light coming on or the wheel heating up. NOTE: I did not fully connect the airbags. Only the 2-wire connector from slipring that has ground as well as that powers the heated wheel, and then the 3-wire connector for the button that turns the heated wheel on/off; and 'yes' I had the 4-wire connector plugged to the heating element :-). Each time, neither the green light came on nor the steering wheel warmed up. With the button pod connected, and pressing the heated wheel button, I disconnected the 4-wire connector that plugs to the heating element and tested for power coming out of it and found only slight power (4 volts) on pin 2.
• or the wheel & heating element. Again, testing just the 4-wire connector going to the heating element for continuity, I now get about 3ohms resistance between pins 1 & 2 and nothing on any other combination.

...Or something else I have not considered.

It would be very helpful to know:

1. What continuity readings should I get when testing only the heated wheel on the 4-wire connector?
2. What voltage should come out of the 4-wire connector that plugs to the heating element? Which pins, (1 and/or 2), should have power?
3. Is there a way to test the little wiring harness?
4. Is there a way to test the heated wheel button pod?
5. Should I rent a mule and have it kick me in the face?

Thank you, all, for your continued support through this challenging affair.

Jay

[racer2086]

Jay,

Testing isn't as easy as measuring voltages at pins. The reason for this is that the wheel will not get heated if it doesn't sense the thermistor built into the element. The car requires feedback from that item in order to give it any power at all to heat up. Second, the electronics control the power to the element to regulate the temperature. It may be done via PWM, so you won't get a fixed voltage going to the element.

If I had to guess, I'd bet both elements were bad, but I don't know what they should read for resistance for you to test them. My recommendation would be to find someone near you with a car with a heated wheel you can test yours in. Or start from scratch -- remove everything and start from the beginning. Get a good positive voltage source, and solid ground, and wire them to the slip ring. Then hook up your connectors as they should be using the equipment you think is most likely to be good.

Where are you getting your power from? If the heating light isn't turning on, there's most likely a power problem or a heating element problem.

[jpilk99]

Jay,

Testing isn't as easy as measuring voltages at pins. The reason for this is that the wheel will not get heated if it doesn't sense the thermistor built into the element. The car requires feedback from that item in order to give it any power at all to heat up. Second, the electronics control the power to the element to regulate the temperature. It may be done via PWM, so you won't get a fixed voltage going to the element.

If I had to guess, I'd bet both elements were bad, but I don't know what they should read for resistance for you to test them. My recommendation would be to find someone near you with a car with a heated wheel you can test yours in. Or start from scratch -- remove everything and start from the beginning. Get a good positive voltage source, and solid ground, and wire them to the slip ring. Then hook up your connectors as they should be using the equipment you think is most likely to be good.

Where are you getting your power from? If the heating light isn't turning on, there's most likely a power problem or a heating element problem.

Thanks Racer.

I believe that both heating elements in the 2 wheels I have are bad. I will work to find a wheel that I KNOW works and test from there.

I assume that little green light will only work when the "system" works, so, as noted above ...I have work to do. Thank you!

Jay

[jpilk99]

Thanks Racer.

I believe that both heating elements in the 2 wheels I have are bad. I will work to find a wheel that I KNOW works and test from there.

I assume that little green light will only work when the "system" works, so, as noted above ...I have work to do. Thank you!

Jay

Wow, this is getting funnier and funnier by the moment. After the last exchange(s) above, I was of the thinking that my 2 steering wheels with the heating element in them we not functioning properly. However, after another trip to the junkyard, I sat in a vehicle that has the heated wheel. I had actually pirated the wiring harness and button pod off that setup earlier this week... So I tested the 4-wire connector and found that it performed JUST LIKE my 2 steering wheels at home. Pins 1 & 4 had very low resistance, between 1 and 2 ...Ohms? No other combination of the 4 wires had continuity.

Ironically, there was another heated wheel laying on the ground, and I tested it as well and it performed as the other 3. I am now of the opinion that all 4 wheels heating element are fine. (Still don't know why, if pins 1 & 2 are the power to the element, why they don't have 0 resistance, but.....).

So; what the heck now? I know I have good POS and NEG. I can't know for sure if the wiring harnesses are okay, but, I can't believe both would be duds. I can't believe all 3 button pods are duds....

The only thing I can think at this point, (and I wish I knew what the flow of electricity is in a good setup), is to try and test - with just the little wiring harness plugged into the Heated Wheel 2-wire Connector at the slip ring, and then try and see where I can find power downstream. If I plug in the button pod, will pressing the button result in there being POS at one/any of the 4-wire connector that goes into the heating element.

[purplecty]

http://www.bimmerboard.com/forums/posts/604838

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